1. Field of the Invention
The invention relates to a lens, more particularly to an adjustable lens device for optical equipment.
2. Description of the Related Art
As shown in FIGS. 1 and 2, a conventional adjustable zoom lens device for a projector includes a fixing seat 1, an adjusting seat 2 sleeved inside the fixing seat 1, a front lens module 3 mounted to a front end portion of the fixing seat 1, and a rear lens module 4 mounted to a rear end portion of the fixing seat 1. The fixing seat 1 is in a form of a tube with a stepped configuration, and is formed with two sets of guide slots 101 extending parallel to an axis, and a set of limiting slots 102 extending along the rim adjacent to the guide slots 101. The adjusting seat 2 is also in a form of a tube with a stepped configuration. The adjusting seat 2 is rotatably mounted inside the fixing seat 1, and is formed with two sets of spirally extending first driving slots 201, and a set of second driving slots 202 that extend spirally in a direction opposite to the first driving slots 201. A set of limiting components 203 is mounted on the adjusting seat 2 adjacent to the second driving slots 202, and extends into the limiting slots 102. The first driving slots 201 and the second driving slots 202 correspond to the guide slots 101. The front lens module 3 includes a sleeve 301 and a front lens set 302 mounted inside the sleeve 301. The sleeve 301 has a set of front guide components 303 passing through the second driving slots 202 and the guide slots 101, and is formed with a set of sliding slots 304. The front lens set 302 includes a set of guide components 305 that extends into the sliding slots 304. The rear lens module 4 includes first and second lens sets 401 and 402, each of which has a set of rear guide components 403 passing through the first driving slots 201 and the guide slots 101.
When a user rotates the adjusting seat 2, the front and rear lens modules 3 and 4 will move in the same or opposite directions along the axis for zooming adjustment by virtue of the second driving slots 202, the first driving slots 201, the guide slots 101, and the front and rear guide components 303 and 403. In another aspect, when the user rotates the front lens set 302, the focus is adjusted.
The aforementioned lens device has the functions of zoom and focus adjustments, and the design of the limiting slots 102 positions the adjusting seat 2 relative to the fixing seat 1 along the axis while limiting the range of angular rotation of the adjusting seat 2. However, the limiting slots 102 are required to be bored through the fixing seat 1, and a plurality of screw holes 203′ are required to be bored through the adjusting seat 2 for fixing the limiting components 203. Therefore, the conventional lens device has many components and a complicated structure that result in a high cost of manufacturing and processing.